1. Field of the Invention
The present invention is concerned with an antimicrobial composition which is useful for inhibiting microbial growth wherever such microbial growth is undesirable, e.g. aqueous systems found in a variety of industrial applications, such as, for example, papermaking and cooling water applications. More particularly, the present invention is concerned with an alkyl guanidine composition and salts thereof that are storage stable at temperatures below 5.degree. C. A process for making the same is also disclosed.
2. Description of the Background Art
As used herein, the phrases "biocide", "antimicrobial", and "inhibiting microbial growth" describe the killing of, as well as the inhibition of or control of, biological growth including, but not limited to, bacteria, yeasts, fungi, and algae. A number of important industries have experienced serious adverse effects from the activity of such biological growth on the raw materials which they employ, on various aspects of their manufacturing activities, or on the finished products which they produce. Such industries include, for example, but are not limited to, the paint, wood, textile, cosmetic, leather, tobacco, fur, rope, paper, pulp, plastics, fuel, oil, rubber and machine industries.
The present invention provides an improved biocide compound, namely an alkyl guanidine composition and salts thereof, which exhibits superior storage stability at low temperatures as compared to alkyl guanidine hydrochloride compounds known in the art. It will be appreciated by those skilled in the art that mineral acid or monocarboxylic acid salts of alkyl guanidines are known for their antimicrobial activity such as disclosed, for example, in U.S. Pat. Nos. 2,867,562, 2,906,595, 3,116,326, 3,142,615, 3,143,459, 3,264,172 and 3,628,941. The acid salts of dodecylguanidine are the best known and widely used compounds of the class.
Dodecylguanidine hydrochloride (DGH) is an alkyl guanidine hydrochloride wherein the alkyl group has a twelve carbon chain. Typically, DGH is synthesized by reacting very pure lauryl amine, i.e. C.sub.12 &gt;98%, with hydrogen cyanamide in hydrochloric acid, water, and isopropyl alcohol (IPA). The DGH produced by this method, however, has poor storage stability. Storage stability of alkyl guanidine antimicrobial compositions has been an ongoing problem, particularly during cold weather. At low temperatures such as, for example, below 5.degree. C. and more particularly below 0.degree. C., and/or during temperature freezing and thawing situations, DGH prepared by this known method tends to precipitate or wax out of solution which presents a severe handling problem.
Another problem associated with DGH as it is currently manufactured is its relatively low flash point, for example less than 38.degree. C. As with any composition containing significant levels of IPA, the potential flammability of DGH is unacceptably high for use in many industrial applications. Attempts to alter the amount of IPA used in DGH production have met with only limited success. For example, DGH formulations with less IPA have a higher flash point and are therefore safer to use, but also have a lower percentage of active alkyl guanidine. DGH formulations with higher amounts of active alkyl guanidine have more IPA and therefore a lower flash point which makes them more flammable. This problem makes the use of DGH prohibitive for many industries which require the use of biocides.
In spite of this background material, there remains a very real and substantial need for an alkyl guanidine antimicrobial composition and process for making the same having improved storage stability at temperatures below 5.degree. C. and a flash point above 38.degree. C. for providing safer handling than other alkyl guanidine salts known in the art.